Highly unlikely to be the ASD relay as that provides batt voltage to the field circuit. If there was no voltage to the field circuit grounding out the other field terminal wouldn't result in the alt charging.
You need to get the pinout diagram for the ECM plug. I have one, but it's on my home pc and I'm out of town until next Mon. That and a multimeter (volts and ohms at least) will let you track this down.
What you are looking for is the 4 pins that provide power and ground to the ecm. There is one with batt+ all the time, one with batt+ key on and 2 ground pins. You check them all with a volt meter and make sure you have correct voltage (no voltage drop, reverse polarity of tester to check grounds) at all pins. Once you have ensured all that is good you can check for continuity to the alt field wire. Check for continuity to the cps. If all those check out I would suspect a bad ecm, but most likely you are going to find a wiring issue.